From my own experience I can confirm that Steam for Windows works great with recent versions of Wine.

By this you can run many naitve Windows games available through Steam using Wine or Play On Linux. Issues and games which won't run, or tweaks needed are best being queried from the Wine Application Database. It may also be worth to have a look at the Steam support forums for issues.

As a rule of thumb: if a game is listed as Platinum you will be able to play it without issues. A game rated as Gold will be playble just fine but may need some tweaks. All other ratings indiciate more or less severe issues.

Performance of games played through Wine varies considerably but many games will just perform fine with only a minor perfomance loss as compared to native Windows. This will also include 3D graphics which is supported through DriectX drivers in Wine.

Sadly however there is no guarantee that any single game you bought will actually run on your specific system. In case a Linux version is available through Steam you will probably better install this version.

It is also possible to connect your Steam account to both, native Steam for Ubuntu, and Steam for Windows run through Wine.